1. Field of the Invention
The present invention relates to Pseudo Noise (PN) code receivers and PN code detection loops used to receive and acquire incoming PN coded signals. More particularly, the present invention relates a novel PN code extractor circuit employed with a PN code receiver and code detector to enhance the strength of the acquired signal.
2. Description of the Prior Art
PN code receivers and code detection loops are known and have been used to receive incoming PN coded signals. The received signal is received at a random time and phase until the slip control circuits slip the PN replica generator code one chip at a time to achieve correlation.
It can be shown that in the prior art a worse case condition with one-half chip offset that the correlation signal is attenuated by 6 decibels when attempting to acquire the received PN code.
It has been suggested that in the prior art that the slip and control circuits could be modified to slip the PN replica code in one-half chip steps. While this known technique does reduce the worst case condition to an attenuation loss of only 2.5 decibels, the search time for correlation is doubled which results in the equivalent addition of 3 decibels for a total loss of 5.5 decibels. Thus, the overall accomplishment by employing a one-half chip steps during search and acquisition is substantially the same as using a one chip search.
It would be highly desirable to provide any type of circuit or system which would result in enhancing the speed of acquisition of a PN code.